I. Related Applications
There are no applications related hereto heretofore filed in this or any foreign country.
II. Field of Invention
My invention relates generally to main frames for automotive vehicles and more particularly to such frames as are formed in a unitary fashion from plastic and fiber materials.
III. Description of Prior Art
The frame of an automotive vehicle, often generically called its chassis, serves the purpose of interconnecting the vehicular wheels, providing a structure that is more or less rigid in bending and torsion, and supporting the other components and occupants of a vehicle. In its origin, chassis design was of a beam type with two parallel spaced elongate beams variously interconnected by cross beaming to provide a rigid but heavy structure, similar to the post and beam structural design of its time.
As more concern was directed toward automotive performance it was realized that the chassis mass had to be lessened in performance designed cars, especially such as for racing. Frame construction then evolved to a tubular type originally comprising the so-called ladder construction, essentially similar to the beam type but using hollow elements. Still later the frame evolved to the tubular box type which provided not only a chassis but also a framework for various peripheral body elements of the vehicle. The box frame provides a strong and rigid skeleton for an automotive vehicle but it is relatively complex, difficult of construction and generally must be specially designed for a particular vehicle to accommodate its body and various other components.
Most recently the three dimensional box type frame, sometimes called a unit body, has further evolved to include structural embodiment of various automotive components within the frame itself, particularly parts of the peripheral body and the passenger compartment floor. This type of construction is obviously more specialized than that of the general box frame and because of this it is more difficult of manufacture in the inception and of repair thereafter. Though the overall frame mass is less with the box construction than with the earlier structures from which it evolved, still the frame mass remains in a substantial range and the repair of such a vehicle that has been accidentally damaged is quite costly, complex and time consuming, if at all possible. In general the box frame construction, and particularly that incorporating body elements, provides little crash protection and little insulative capability as to either heat or sound, all to make the design less desirable in an ordinary automotive vehicle.
Design desires for rigidity against bending and torsion in automotive frames have largely been brought about because of the interrelation of these features with suspension systems for the vehicular wheels. In general as the chassis becomes less rigid, the wheel suspension systems must become stiffer. Most automotive vehicles in practical design result in compromise between the stiffness of the chassis and the stiffness of the suspension system to allow proper load carrying capacity, proper steering of the vehicle and reasonable passenger comfort. In general, however, with the traditional types of frame systems described, more emphasis has been placed on frame rigidity than on suspension stiffness and because of this auto frames have remained fairly complex in structure and substantial in mass.
The instant invention seeks to alleviate these problems and incidents associated with them by providing a chassis or underframe essentially of the ladder type but formed of composite plastic and fiber materials. My frame is lighter in weight, from three to six times, than traditional metallic automotive frames. Physically my frame is of a unitary construction that is simple to form and repair, generally without any requirement of highly skilled craftsmanship as is the case with metallic tubular frames. The frame mechanically provides greater strength and rigidity to resist both torsional and bending moments than the traditional metallic frames of either the beam or tubular types that are commonly used in the present day automotive arts. The composite plastic material is quite durable, provides good dynamic vibration absorption and has a greater fatigue resistance than ordinary metallic structures. Impact damage resistance of my frame is greater than that of metallic frames and the overall crash protection is also greater because the frame design provides a progressive crash barrier to absorb severe impact. The frame itself provides substantial insulation to the point of being a barrier to both sound and heat. The material from which the frame is formed is corrosive resistant by nature and is unaffected by normal automotive substances and chemicals. The frame is of substantially lower cost than a comparable metallic frame because of the nature of its materials and their formation.
In design theory, particularly in consideration of the relationship between frame rigidity and suspension stiffness, my frame allows substantially the same relationship as exists in present day vehicle construction. My frame is as rigid as the modern day tubular frame and because of this requires no more stiffness in wheel suspension than do present day tubular frames. In fact, if desired, the wheel suspension may be somewhat less stiff with my frame than with other present day frames to generally allow a more comfortable ride for passengers while maintaining the same driving and cornering characteristics of present day vehicles.
My frame in general provides a larger cross-sectional area but not necessarily a larger peripheral dimension or area than traditional tubular metallic beams. Any peripheral size differential generally provides no disadvantage, however, since my frame merely occupies unused space within the volume enclosed by the traditional vehicle. My beam structure itself though provides several advantages over metallic frames which are only enhanced by any larger peripheral area. In the formation process, if a foamed core be used, the material itself tends to increase in density in proportion to the distance from the center of the element, being most dense at the periphery, which tends to provide greater strength in a position where it is most beneficial. In addition the stronger fiber structure is at the periphery of the frame elements to there perform substantially the same physical function as a hollow or tubular type element. The cross-sectional size of my frame and the material from which it is formed tend to provide substantial shock absorption which is not provided by traditional metallic frames. The rigidity of the whole frame is materially increased because the most rigid portions of the frame are at its periphery and frame strength is increased because the core tends to distribute bending and shear forces over substantial area of the periphery.
In addition the frame elements can define a structure with orifices and a closed periphery to add to the rigidity of the total frame and its shock absorbent powers. The mounting of various automotive components upon my frame is by means of brackets carried by plates structurally embodied within the frame elements. This mounting is quite as simple as the mounting of similar components upon the traditional frames of present day commerce.
My invention in accomplishing these ends is distinguished both structurally and functionally from the vehicular frame structures heretofore known, either individually or in any combination.